Key Laboratory of Eutrophication and Red Tide Prevention of Guangdong Higher Education Institutes, College of Life Science, Jinan University, Guangzhou, China.
School of Life Sciences, Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.
J Exp Bot. 2021 Apr 2;72(8):2918-2932. doi: 10.1093/jxb/erab026.
Phosphorus (P) limitation affects phytoplankton growth and population size in aquatic systems, and consequently limits aquatic primary productivity. Plants have evolved a range of metabolic responses to cope with P limitation, such as accumulation of purple acid phosphatases (PAPs) to enhance acquisition of phosphates. However, it remains unknown whether algae have evolved a similar mechanism. In this study, we examined the role of PAPs in the model microalga Phaeodactylum tricornutum. Expression of PAP1 was enhanced in P. tricornutum cells grown on organophosphorus compared to inorganic phosphate. PAP1 overexpression improved cellular growth and biochemical composition in a growth-phase dependent manner. PAP1 promoted growth and photosynthesis during growth phases and reallocated carbon flux towards lipogenesis during the stationary phase. PAP1 was found to be localized in the endoplasmic reticulum and it orchestrated the expression of genes involved in key metabolic pathways and translocation of inorganic P (Pi), thereby improving energy use, reducing equivalents and antioxidant potential. RNAi of PAP1 induced expression of its homolog PAP2, thereby compensating for the Pi scavenging activity of PAP1. Our results demonstrate that PAP1 brings about sequential regulation of metabolism, and provide novel insights into algal phosphorus metabolism and aquatic primary productivity.
磷（P）限制会影响水生系统中浮游植物的生长和种群规模，从而限制水生初级生产力。植物已经进化出一系列代谢反应来应对 P 限制，例如积累紫色酸性磷酸酶（PAPs）以增强磷酸盐的获取。然而，藻类是否已经进化出类似的机制尚不清楚。在这项研究中，我们研究了模型微藻三角褐指藻中 PAPs 的作用。与无机磷酸盐相比，在有机磷上生长的三角褐指藻细胞中 PAP1 的表达增强。PAP1 的过表达以生长阶段依赖的方式改善了细胞生长和生化组成。PAP1 在生长阶段促进生长和光合作用，并在静止阶段重新分配碳通量以进行脂生成。发现 PAP1 定位于内质网，它协调参与关键代谢途径和无机磷（Pi）转运的基因的表达，从而提高能量利用、还原当量和抗氧化能力。PAP1 的 RNAi 诱导其同源物 PAP2 的表达，从而补偿 PAP1 的 Pi 清除活性。我们的结果表明，PAP1 带来了代谢的顺序调节，并为藻类磷代谢和水生初级生产力提供了新的见解。
